Reference
Paper sizes
A short, practical reference for the paper sizes you actually use. The ISO A-series is the international standard; US Letter and its relatives are still dominant in North America. Pick a size below for full dimensions and pixel resolutions at common DPI values.
Want everything on one page? The complete size chart lists all 48 standard sizes — ISO, US, ANSI and ARCH — with a downloadable PDF. Working in PDF or InDesign? See every size in points.
Two systems, one decision
Every size on this page belongs to one of two families. The ISO A-series is a single recursive rule: start from a sheet of one square metre at a 1 : √2 ratio, halve it along the long edge, repeat — the diagram on the right is the entire system in one picture. Because the ratio never changes, an A4 layout scales onto A3 or A5 without cropping, booklets fold cleanly, and photocopiers can enlarge between sizes with a single fixed percentage.
The US sizes obey no such rule — they are independent inch-defined sheets standardised long before ISO 216 existed. Their compensation: inch definitions produce exact whole-pixel values at every common DPI (Letter at 300 DPI is precisely 2550 × 3300), which the millimetre-defined ISO sizes never manage. Choosing is simple geography: audience in North America → Letter family; anywhere else → A-series; documents that must survive both → design inside the shared 210 × 279.4 mm footprint.
The A-series halving rule, drawn to exact scale.
ISO 216 A-series
The international standard
Each A-size is the size above it halved along the long edge, which keeps the 1 : √2 proportion constant throughout the series. In practice the halves are rounded down to whole millimetres, so an A5 sheet is about 0.3 % smaller than a mathematically exact half of A4 — invisible in use, but the reason the numbers are 148 rather than 148.5.
A0
33.11 × 46.81 in841 × 1189 mm
The base sheet of the ISO 216 A-series. Each smaller A-size is the one above it halved along the long edge, then rounded down to whole millimetres.
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A1
23.39 × 33.11 in594 × 841 mm
Half of A0. A common indoor poster size and a frequent choice for technical drawings.
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A2
16.54 × 23.39 in420 × 594 mm
Half of A1. Often used for medium posters and presentation boards.
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A3
11.69 × 16.54 in297 × 420 mm
Twice the area of A4. The largest size most office printers handle.
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A4
8.27 × 11.69 in210 × 297 mm
The everyday office and document size used across most of the world.
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A5
5.83 × 8.27 in148 × 210 mm
Half of A4. A practical size for notebooks, leaflets and small flyers.
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A6
4.13 × 5.83 in105 × 148 mm
Half of A5. Common for postcards, pocket notes and small invitations.
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US sizes
North American paper
Defined in inches rather than millimetres. Common in the US, Canada, parts of Mexico and the Philippines.
US Letter
8.5 × 11 in215.9 × 279.4 mm
The standard office paper in the United States, Canada and a few other countries. 8.5 × 11 in.
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US Legal
8.5 × 14 in215.9 × 355.6 mm
Same width as Letter but longer (8.5 × 14 in). Used for legal forms and longer documents.
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Tabloid / Ledger
11 × 17 in279.4 × 431.8 mm
Twice the area of Letter. 11 × 17 in. Used for newsletters, posters and spreadsheets.
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When to use ISO vs US sizes
If you are designing for a worldwide audience, ISO sizes (especially A4 and A5) reach a much larger share of printers and print shops. If your audience is primarily in North America, sticking with US Letter avoids reflowing layouts that were optimised for 8.5 × 11 in.
Mixing sizes in one document
A4 (210 × 297 mm) and US Letter (216 × 279 mm) are close enough that text often reflows cleanly, but the proportions are subtly different. For graphics that must align with the paper edge, design for the exact target size from the start rather than converting later.